<!DOCTYPE html>
<html>
<head lang="en">
    <meta charset="UTF-8">
    <title></title>
    <style>
        .box{
            width: 300px;
            height: 100px;
            margin:100px auto;
            border-radius: 10px;
            background:url(images/paopao.png) no-repeat left top,
            url(images/paopao.png) no-repeat right bottom;
            background-color: blue;

            /*添加过渡*/
            transition:all 2s;
        }

        .box:hover{
            background-position: left bottom,right top;
        }
    </style>
</head>
<body>
    <div class="box"></div>
</body>
</html>